Slotted nose hydroski



July 11, 1961 M. l. HAAR ETAL SLOTTED NOSE HYDROSKI Filed June 6, 1960MARVIN H441? DEN/W5 D. H. LUEDERS ROBERT E PROWSE DAN/EL SAV/TSKY ROBERTL. VA/VDYGK 2,991,745 SLOTIED N E HYDRQSKI Marvin I. Haar, Baltimore,Md, Dennis D. H. Lueders, Bogota, and Robert E. Prowse, Teaneck, N.J.,Danie] Savitsky, Jackson Heights, N.Y., and Robert L. Van Dyck, FortLee, N..I., assignors, by mesne assignments, to the United States ofAmerica as represented by the Secretary of the Navy Filed June 6, 1960,Ser. No. 34,343 3 Claims. (Cl. 114-665) The present invention relates toimprovements in hydroskis and more particularly to a new and improvedhydroski having a slotted nose for reducing unporting spray formedduring emergence of a hydroski attached to an aircraft.

In the operation of hydroski aircraft it has been found that a largeburst of spray is thrown up at the nose of the ski as it breaks throughthe water surface and that frequently this spray interferes with theaerodynamic surfaces or propulsive system of the aircraft to an extentwhich can seriously hamper or prevent take-off. In the past, in order toreduce emergence spray, the ski nose was generally kept pointed. To beeffective a long narrow point is required. This introduces structuralproblems which outweigh the advantages in spray reduction.

The general purpose of the invention is to provide a hydroski whichembraces all the advantages of presently employed hydroskis withouthaving emergence spray. To attain this, the present invention consistsof the formation of an opening or slot which passes from the uppersurface to the lower surface of the hydroski. The slot is arranged anddimensioned so as to substantially reduce emergence or unporting spray.

An object of the present invention is to provide an improved hydroskifor reducing emergence or unporting spray.

Another object is to provide an improved hydroski for reducingvariations in hydrodynamic forces and moments during emergence.

A further object of the invention is the provision of an improvedhydroski having improved hydrodynamic characteristics while remainingstructurally sound.

Other objects and many of the attendant advantages ofthis invention willbe readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 shows an elevation view of a preferred embodiment of theinvention;

FIG. 2 shows a plan view of a preferred embodiment of the invention;

FIG. 3 shows a section of the invention taken on the line 3-3 of FIG. 1looking in the direction of the arrows;

FIG. 4 shows a section of the invention taken on the line 4-4 of FIG. 1looking in the direction of the arrows;

FIG. 5 shows a section of the invention taken on the line line 5-5 ofFIG. 1 looking in the direction of the arrows;

FIG. 6 shows a section of the invention taken on the line 6-6 of FIG. 1looking in the direction of the arrows; and

FIG. 7 shows a section of the invention taken on the line 7-7 of FIG. 1looking in the direction of the arrows.

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIG. 1 a hydroski 11 submerged beneath a water line12. Said hydroski has a nose portion 13 connected to the bow of bodyportion 14 which has a deck 16, a keel 17 and a chine 18. The noseportion 13 is especially suited to reduce a particular type of spraycalled unporting spray which is associated with emerging hydroskis. Asforward speed of the hydroski 11 is increased during take-01f, ahydrorates Patent 0" 2,991,745 Patented July 11, 1961 dynamic lift forcedevelops on the ski which causes the ski-nose 13 to come up through thewater surface. Normal ski noses produce a large quantity of spray duringemergence or unporting. Nose 13, however, is of an improved constructionto reduce such spray. In FIG. 1 nose portion 13 is illustrated as havinga top hood 19 which in turn has a leading edge 21. The hood 19 isdownwardly curved and is relatively thin sectioned as seen in FIGS. 3through 5. The curved down hood 19' and leading keel portion 22 minimizethe disturbance created at the leading edges 21 and 23 and deflect anyundesirable flow to the sides aft of the nose13. Longitudinally rearwardof hood 19 a leading keel portion 22 forms the bottom portion of noseportion 13. Keel portion 22 has a leading edge 23. A slot $4 is formedin nose portion 13 so as to pass from bottom surface or keel 17 of thehydroski to the top surface or deck 16 of the hydroski. The slot 24 isplaced as far forward as possible and in such a way that top hood '19 isvery thin. The slot '24 is made as Wide as is structurally feasible andthough its longitudinal dimension is dependent upon operating conditionsit will be approximately one-half of the ski beam B. Furthermore, theslot 24 is slanted so that the upper end is further aft than the bottomend. The degree of slant is such that the forward wall 25 of the slot isapproximately in a horizontal plane when the ski emerges. Fifteendegrees has been found to be suitable degree of slant or trim angle fora workable design.

The operation of the improved hydroski is as follows: In order to betterindicate the invention the operation will initially be compared with thehydrodynamic characteristics of an ordinary hydroski. During theemergence of the usual type of hydroski a high pressure occurs at theforward end of the ski. This pressure causes a flow of water upvertically in the bow region of the ski which forms the emergence orunporting spray. The hydrodynamic action during emergence of theimproved hydroski set forth above is as follows. As forward speedincreases a hydrodynamic lift force develops on the ski and the nose 13approaches the free water surface 12, the water is disturbed by theleading edge 21 of hood 19, channeled into the slot 24 and washed alongthe deck 16 of the ski, instead of being thrown up in the form of spray.The water emerging from slot 2.4 is not thrown up as spray for tworeasons: first, because the lifting or planing of the ski effectivelyplaces slot 24 in a horizontal position so that water rushes through theslot unimpeded and with no distance to fall; and second, because of thelaw of fluiddynamics known as the Coanda effect which causes fluids toflow smoothly along convex surfaces. As the ski continues to rise theleading edge 23 of keel portion 22 intersects the free Water surface andgenerates a spray. This spray is reflected down by hood 19. Thus, duringall phases of emergence unporting spray is effectively reduced so as toavoid resistance and physical damage to the craft being supported by thehydroskis.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A hydroski or the like comprising a body portion having a deck, achine and a keel, a nose portion attached to the forward end of saidbody portion, said nose portion having a top hood and a leading keelportion, said nose portion also having a rearwardly slanting slot formedtherein between said top hood and said keel portion whereby emergencespray is suppressed.

2. A hydroski or the like comprising a body portion having a deck, achine and a keel, a nose portion attached to the forward end of saidbody portion, a hood on said nose portion, a keel portion on said noseportion, said nose portion having a slot formed therein slanted at 15 sothat the upper end is further aft than the bottom end, said slotcommencing between said hood and said keel portion and terminating atsaid deck whereby emergence spray is suppressed.

3. A hydroski or the like comprising a body portion having a deck, achine and a keel, a nose portion attached to the forward end of saidbody portion, a downwardly curved hood on said nose portion, a keelportion on said nose portion located aft of said hood, said nose portionhaving a slot formed therein, said slot slanted at 15 so that the upperend is further aft than the bottom and the degree of slant being suchthat the forward wall of said slot is approximately in a horizontalplane when the ski emerges, said slot commencing between said hood andsaid keel portion and terminating at said deck whereby on 4 initialemergence of said hydroski said hood channels water into said slot andalong said deck and on higher emergence said keel portion creates spraywhich is refiected downwardly by said hood so as to minimize emergencespray.

References Cited in the file of this patent UNITED STATES PATENTS1,133,342 Ursinus Mar. 30, 1915 1,269,397 Curtiss June 11, 19181,750,593 Hangan Mar. 11, 1930 2,162,705 Diehl June 20, 1939 2,919,669Kikuhara Jan. 5, 1960 2,931,134 Nevitt Apr. 5, 1960 2,940,091 Fifer June14, 1960

